The present invention relates to spring assist systems for moving the ramps of heavy equipment trailers from positions of loading and transport.
Heavy equipment trailers usually require a ramp system for the loading of equipment. Many trailers of this type are equipped with ramps that can pivot from a position of transport, where the ramps are folded back and rest on the trailer when not in use, to a position for loading of equipment. Because the equipment to be transported is typically quite heavy, the loading ramps must necessarily be of solid construction and therefore are heavy themselves. This makes it difficult for the operator to pivot the ramps into position.
There exist trailer ramp spring assist systems in the prior art. Most, however, serve only to raise the ramp to the transport position and do not assist the lowering of the ramp from the transport position to the loading position. One solution that solves both problems is a system incorporating a hydraulic system to provide the needed power, but it is costly and is difficult to apply to a double-hinged free floating ramp system.
Other systems use a single spring that functions to assist movement of the ramp through both forward and reverse pivot directions. This type of operation imparts both a coiling and uncoiling action to the spring. The uncoiling action on the spring tends to distort the shape of the spring after a period of time, which will have a detrimental effect on the functioning capability of the spring.
An additional consideration and obstacle to overcome is the installation of a ramp that will have a great deal of spring force against it when it is in either of its two normal positions of loading or transport. There must be a way to safely install the springs with simple tools while the ramp is laying on the ground or on the trailer. In addition, there must be a means for adjusting the ramps laterally. The problem exists that if all the springs remain loaded, the ramps will be "bound up" and resist lateral adjustment.
Another consideration is the ability to vary the degree of pre-loading of the spring. Spring assist systems in other areas of application have means to pre-load the spring, or to vary the stress placed thereon. This is usually done by manually stressing the spring itself to a desired level. The drawback to this is that a great deal of force is sometimes required to positively turn the spring to reach the desired level of stress. If a large spring is used, which is generally the case with trailer ramps, it may be very difficult to pre-load the spring without heavy tools.